One of the outstanding problems in the study of shale gas (SG) formations is the in-situ pressure of the gas. This parameter is proportional to the amount of gas that can be recovered from the formation and thus has important economic implications. Conventional methods such as drawing fluid at known pressure differentials using a sampling tool are not effective in cases when the permeability is too low, such as in shale gas and other formations where the pores are generally not interconnected. Currently no method is available for making this measurement in either the borehole or the laboratory.